Two Threats, One Blind Turn: The Tricolor, Kariba and Clary Collision

Three Vessels, Full Radar Data, and Total Silence

On the night of 14 December 2002, in thick fog reducing visibility to less than 100 metres, three vessels converged at the intersection of the Dover Strait Traffic Separation Scheme. Kariba, a 580ft container ship, was making 16 knots westbound. Tricolor, a 627ft car carrier, was half a mile off Kariba's starboard quarter, overtaking at 17.9 knots. Clary, a 455ft bulk carrier, was approaching from the south on a near-90-degree crossing course at 13 knots.

Every vessel had full course, speed and CPA data on the other two, the entire time, on radar. This was not a technology failure. In the fifteen minutes before the collision, none of the three vessels sounded a fog signal or attempted VHF contact with any of the others.

One Turn, Two Problems

Kariba's bridge team tracked Clary approaching from the south and expected her to turn to starboard as the give-way vessel. When Clary showed no sign of altering course, Kariba opened the CPA herself — helm to starboard, 10 degrees, then increasing to 20, then hard over. The turn was intended to solve the Clary problem. It was never re-checked against Tricolor's position.

Tricolor, still overtaking and still committed to her track, was now inside the arc Kariba's turn swept through. Kariba's bulbous bow struck Tricolor's port side. Tricolor capsized and sank rapidly — a later supplementary BEA-mer investigation found progressive flooding through a gash in the hull and into the engine room via watertight doors on decks 9 and 11 that were unlocked, ajar, or derailed at the time.

What the Investigation Found

BEA-mer's investigation, upheld on appeal against an initial finding that placed sole blame on Kariba, concluded that all three vessels — Kariba, Tricolor and Clary — had committed at least one violation of the COLREGS, and that each violation was a cause of the collision. Contributing causes included dense fog cutting visibility to under 100 metres, excessive speed for the conditions (Tricolor was making 17.9 knots while overtaking in fog), and non-compliance with Rule 13 (overtaking) and Rule 6 (safe speed in restricted visibility) within the TSS.

The Real Failure Wasn't Radar

Each bridge team could see the other two vessels the entire time. What none of them did was talk to each other, or re-confirm a plotted position before manoeuvring around it. Kariba's turn to solve one threat blindsided her to a second, already-known threat that hadn't moved out of the way — it had simply moved out of the bridge team's attention.

Recommended Actions

1. In any multi-vessel close-quarters situation in restricted visibility, use VHF and/or sound signals to confirm the other vessels' intentions rather than assuming compliance with the give-way/stand-on roles
2. Before completing a manoeuvre made to resolve one collision risk, independently re-fix the bearing and range of every other vessel that manoeuvre will affect
3. Maintain a safe speed appropriate to restricted visibility — a speed that allows the vessel to be stopped within a distance appropriate to the prevailing circumstances
4. Internal watertight doors below the waterline should be kept closed and verified closed at sea, not left unlocked or ajar, given how directly this affected Tricolor's survivability once holed